Well completion method

ABSTRACT

A downhole well tool having at least one aperture therein for communication between the interior and exterior thereof and means for sealably opening and closing said aperture, the means for opening said aperture having means for receiving an opening plug, the opening plug being adapted to receive a bypass wiper, and the means for closing the aperture being adapted to receive a shutoff plug. A well completion method utilizing the tool above-described wherein residual liquid outside the tool is removed by passing a second liquid into the interior of the tool, through the aperture of the tool, and up the annulus between the tool and the wellbore. The second liquid is followed by a third liquid. The third liquid is displaced into said annulus through said aperture by cement, after which the tool is closed.

United States Patent [191 Schuh Feb. 12, 1974 WELL COMPLETION METHODPrimary Examiner-Stephen J. Novosad Inventor: Frank J. Schuh Dallas TeXAttorney, Agent, or FzrmRoder1ck W. MacDonald [73] Assignee: AtlanticRichfield Company, New

York, NY. [57] ABSTRACT Filedi m 1972 A downhole well tool having atleast one aperture 21 A L N 313,991 therein for communication betweenthe interior and I I pp 0 exterior thereof and means for sealablyopening and closing said aperture, the means for opening said aper- [52]U.S. Cl. 166/291, l66/DIG. 1 {me having means for receiving an openingplug, the [51] Int. Cl E2lb 33/16, E2lb 21/00 opening plug being adaptedto receive a bypass wiper, Field of Seal'dl166/291, and the means forclosing the aperture being adapted 1 to receive a shutoff plug. A wellcompletion method utilizing the tool above-described wherein residualliq- [56] References Cited uid outside the tool is removed by passing asecond UNITED STATES PATENTS liquid into the interior of the tool,through the aper- 2 249 511 7/1941 Westall 166/291 of the and theannulus between the 2:848:05] 8/1958 Williams... 166/291 and theWellbore- The Second liquid is'followed y 9 3,213,940 10/1965 w H 291 Xthird liquid, The third liquid is displaced into said an- 3,l30,7834/1964 Orr 166/289 X nulus through said aperture by cement, after which3,653,441 4/1972 Tuttle 1 166/291 the {00] is closed. 3,730,267 5/1973Scott 166/291 X 9 Claims, 4 Drawing Figures PAIfmmrgntemm sum 1 or 2WELL COMPLETION METHOD BACKGROUND OF THE INVENTION Heretofore, inplacing cement between the exterior of casing in a wellbore and the wallof the wellbore, the prior art has employed a bypass plug through whichcement can be passed to fill up a lower interval in the annulus betweenthe casing and the wellbore. The bypass plug is followed by a shutoffplug for the lower interval that has been cemented. The shutoff plug isin turn followed by an opening bomb which will open a port above saidcemented interval so that cement can be placed in the annulus above saidcemented interval. Lastly, a shutoff plug is employed to close saidport. Such apparatus is fully and completely disclosed in the CompositeCatalogue of Oil Field Equipment and Services, published by WORLD OIL,Gulf Publishing Company, Houston, Tex., 1964, Vol. 2, page 2,154, 26threvision, the disclosure of which is incorporated herein by reference.

Although this apparatus and the method for using same works quite wellfor conventional completions, in permafrost areas, after a well has beendrilled with a freezable fluid such as a water-base drilling fluid, itis desirable to displace the .freezable fluid with a nonfreezable fluidso that any liquid left in the well after completion will not freezeinto a solid. The abovedescribed prior art apparatus and method foremploying same does not accommodate the displacement of a freezableliquid, particularly when the freezable fluid is heavier than thenon-freezable displacement fluid. It is extremely difficult to displacea heavier liquid with'a lighter liquid and to substantially completelyremove the heavier liquid since the lighter liquid will tend to fingerthrough the heavier liquid thereby leaving por- BRIEF SUMMARY OF THEINVENTION By'this invention a tool is employed which is particularlyadapted to allow for displacement of residual or first liquid from awell. This first liquid can be quite heavy, e.g., the water-basedrilling fluid with which the well was drilled, and is displaced fromthe well by a washing step with a second liquid. The second liquid,which can be freezable, is displaced with a third liquid. Between thesecond and third liquids a bypass wiper is employed, the bypass wiperbeing received by the opening plug in the tool. Thereafter the thirdliquid, which can be a nonfreezable liquid, is displaced into theannulus between the toolv and the wellbore by cement.

The tool of this invention allows the displacement of a light secondliquid with a heavier-third liquid down the interior of a pipe stringwithout substantial mixing of the second and third liquids due to theuse of the bypass wiper.

This invention also applies to a method as abovedescribed and whichutilizes said tool in the manner described so that the exterior annulusof the tool and any piping, e.g., casing, connected to the tool containseither cement or non-freezable liquid, substantially no freezable liquidbeing left. Further, the substantially complete displacement of heavyfirst liquid is achieved withoutusing an even heavier second or thirdliquid, the second liquid actually being lighter than the first liquidand the third liquid actually being no heavier than the first liquid.

Accordingly, it is an object of this invention to provide a new andimproved method and apparatus for completing a well. It is anotherobject to provide a new and improved method and apparatus for completinga well in permafrost. It is another object to provide a new and improvedmethod and apparatus for cementing a well. It is another Object toprovide a new and improved method and apparatus for displacing undesiredresidual liquid from a well. It is another object to substantiallycompletely displace residual liquid from a well using liquids that areno heavier than said residual liquid. I

Other aspects, objects and advantages of this invention will be apparentto those skilled in the art from this disclosure, and the appendedclaims.

DETAILED DESCRIPTION OF THE INVENTION FIGS. 1 through 4 show a toolembodying this invention as used in the method of this invention.

More specifically, FIG. 1 shows the earth 1 having a wellbore 2 therein.The tool according to this invention is shown generally at 3 and isspaced inwardly from the wellbore wall 4 to provide an annulus 5 whichis between the exterior of tool 3 (including associated casing) and wall4. Tool3 is disposed between an upper casing string 6 and a lower casingstring 7, the tool being composedof an annular housing 8 having at leastone aperture 9 therein so that communication can be established betweenthe interior 10 of the tool and annulus 5. Housing 3 contains aninternal recessed portion 11 which carries upper and lower annularsleeve means 12 and 13, respectively. Annular recess 11 is sized so thatthe inner surfaces 12' and 13' of sleeves l2 and 13, respectively, donot extend into interior l0 beyond the inner surface 8' of housing 8.

Sleeve means l3 is fixed in place over aperture 9 by shear means 14 andsealably isolates interior 10 from annulus 5 by means of seal means 15.Sleeve 13 has a seat 16 upon which rests an annular opening seat 17.Seat 17 is adapted to receive an opening plug as shown in FIG. 2 forshearing shear means 14 and for sliding sleeve 13 downwardly until itabuts stop shoulder 18 thereby opening aperture 9 for communicationbetween interior l0 and annulus 5. Sleeve 12 is carried in recess 11 bya shear means 19 and also carries seal means 20 which is designed tosealably shut off aperture 9 from annulus 5 when sleeve 12 is slid downto cover aperture 9. Sleeve'12 carries annular closing seat 21 which isadapted to receive a shutoff or closing plug (wiper) as shown in FIG. 4.

Upper casing 6 can extend to the surface of the earth or be connected toother casing sections which do extend to the surface of the earth andwhich are supported somewhere above tool 3. Lower casing 7 terminates at22 so that a fluid can pass from interior 10' around bottom 22 and intoannulus 5 as shown by arrow 23, this fluid passing downwardly from thesurface Of the earth in interior 10 as shown by arrow 24. For example,lower casing end 22 can be connected to a conventional float collar andfloat or guide shoe to allow a conventional first stage cementingoperation to be carried out to emplace cement between the casing andwellbore. The first stage cement will not normally rise as high as tool3 but will stop below tool 3. However, first stage cement can reach toor above tool 3 but the excess cement which reaches tool 3 must becirculated out of the wellbore before it hardens.

With tool 3 in the configuration shown in FIG. 1 aperture9 is sealablyclosed by sleeve 13 so that any fluid in interior 10 cannot pass throughaperture 9 but rather must pass down around end 22 of casing 7. Cementcan be passed through interior 10 around end 22 and upwardly in annulus5 to a point below aperture 9. In this way the annulus between casing 7and wellbore wall 4 can be sealed with cement as shown by 24 in FIG. 2.

FIG. 2 shows the tool of FIG. 1 after cement has been displaced intoannulus 5 up to point 26 which is below aperture 9 so that cementextends from below seat 17 around and under end 22 and up to point 26.

In FIG. 2 opening plug 27 has been passed from the earths surfacethrough interior 10 until it abuts seat 17 at shoulder 28 in a sealingmanner as shown by seal means 29. When opening plug 27 engages seat 17it shears shear means 14 thus moving sleeve 13 downwardly away fromaperture 9 and opening aperture 9 for communication from interior 10 tothe remainder of annulus 5 which does not contain cement.

In the conventional drilling process, interior l and annulus as shown inFIG. 1 are substantially filled with water-base drilling fluid so thatin FIG. 2 all of interior l0 and annulus 5 above plug 27, seat 17, andcement top 26 still contains residual water-base drilling fluid or someother type aqueous liquid. In the case where the residual first liquidjust referred to is a drilling fluid it is normally a heavy fluid inthat it has been weighted with various materials such as barite to giveit weight during drilling for known reasons. Thus, in the normalsituation not only is the residual liquid in interior and annulus 5 ofFIG. 5 freezable, but it is also a relatively heavy liquid which makesit more difficult to displace from interior l0 and'annulus 5.

By this invention a second or wash liquid is passed from the earthssurface downwardly through interior 10 as shown by arrow 30, outwardlythrough aperture 9 as shown'by arrow 31, and upwardly through annulus 5back to the earths surface. This second liquid is for washing the firstliquid out of the well. Since the second liquid is a wash liquid, it canbe used in large volumes and can be substantially lighter than the firstliquid. For example, the second'liquid can-be water (salt or sweet)which is lighter than conventional water-base drilling fluid but is usedin large amounts to minimize the amount of water-base drilling fluidleft by the lighter second fluid by-passing parts of the first heavierfluid. Thus, the second liquid is normally lighter than the first liquidand also lighter than the third liquid.

The second liquid is followed by a bypass wiper (plug) which is shown as32 in FIG. 3. The prior art tools and apparatus do not provide for thissecond liquid or wash step. Nor does the prior art provide for the useof bypass wiper 32.

Wiper 32 is shown to have a projection 33 on its lower end which mateswith a corresponding depression 34 in opening plug 27. Projection 33 isuseful to help keep wiper 32 from being tipped to one side when in theposition shown in FIG. 3 but is not essential to the invention.

After the second liquid wash has been performed and bypass wiper 32seated on opening plug 27 as shown in FIG. 3, substantially only thesecond (wash) liquid'is present in interior It) and annulus 5. Thissecond liquid is then displaced by the introduction into interior 10 ofa heavy, nonfreezable liquid such as an oil-base drilling fluid orpacker fluid which passes downwardly as shown by arrow 40, around vanes41 of bypass wiper 32 as shown by arrow 42, through aperture 9, andupwardly into annulus 5 as shown by arrow 43. Since this third liquid isheavier, e.g., has a higher weight per unit volume, than the secondliquid there is no problem of fingering through or by-passing of thesecond liquid when being displaced by this third liquid. Since wiper 32is used there is substantially no mixing between the second and thirdliquids. Therefore, substantially all of the second or wash liquid,which can be freezable, is removed by the nonfreezable third liquid, andall that remains in interior 10 and annulus 5 at that time isnonfreezable liquid. The third liquid is also preferably more viscousthan the second liquid. The third liquidis also preferably no heavierthan, still more preferably lighter than, the first liquid.

After the emplacement of the nonfreezable liquid, cement is passeddownwardly, through aperture 9, and upwardly into annulus 5 asrepresented by arrows 40, 42 and 43 so that annulus 5.is filledwith'cement. However, should any liquid in annulus 5 be bypassed bycement and therefore trapped in the annulus, this liquid will benonfreezable so that no damage is done should the portion of annulus 5in which the nonfreezable liquid is trapped be adjacent a permafrostportion of the well-bore. The cement is followed by a shutoff or closingwiper (plug) which contacts shoulder 45 of seat 21.

The shutoff wiper is shown in FIG. 4 as element 46 and upon contact ofsame with seat 21 shears shear means 19 and forces sleeve 12 overaperture 9.

As shown in FIGS. 1 through 3 the lower portion of sleeve 12 has anannular cutout portion 47 between sleeve 12 and housing 8 therebyleaving a projection 48 which telescopes over sleeve 13. Seal means 20of projection 48 seals with the interior surface of sleeve 13 while theupper seal means 20 on sleeve 12 seals with the interior surface ofhousing 8. Sleeve 12 thereby effectively seals off communication betweeninterior l0 and annulus 5. Annulus 5 is now substantially completelyfull of cement as is interior 10 below shutoff wiper 46 and even aboveshutoff wiper 46 in that a small amount, for example one barrel, ofcement is sometimes left above the shutoff wiper.

Elements 46, 21, 32, 18, and 34 as well as the cement surrounding sameare all drillable so that all of this material left in interior 10 canbe drilled out thereby leaving only casing strings 6 and 7 and tool 3(elements 8, 12, and 13) present during subsequent production of gasand/or oil through interior 10. Casing strings 6 and 7 and tool 3 arecemented in place by the cement extending below bottom 22 and in annulus5.

The first liquid employed in this invention can be any suitable liquidas can the second liquid but are preferably aqueous since such liquidsare less expensive and oftentimes easier to handle. The second liquidcan even be fresh or salt water locally available and can containvarious chemicals such as thinning agents like sodium acidpyrophosphate. The thinning agent will be transrnitted to the firstliquid to thin same and, because of its reduced viscosity therefrom,render the first liquid more easily washed out by the second liquid.Since the second liquid is just a wash liquid it can be lighter, e.g.,have a lower specific gravity than the first liquid without fear ofleaving freezable liquid in the well.

Bypass wiper 32 is employed between the second liquid and the thirdliquid to prevent the as heavy or heavier third liquid from channelingor fingering into the lighter second liquid as the third liquid passesdown through interior 10 and upwardly in annulus 5 displacing the secondliquid before it. The third liquid can have a freezing depressant liquidas various salts, e.g., sodium chloride, sodium sulfate, and the like.The salts will be passed to any second liqaud or even first liquid thatmay remain behind. The salts being passed to these first and secondliquids act as freeze point depressants for these liquids so that shouldany minute amount of water he left in interior 10 or annulus 5, there isfreezing point depressant available to prevent even this minute amountof residual water from freezing. Further,

the third liquid can contain conventionaloil-wetting agents to make allthe metal parts in the tool and the surfaces'of casing string 6 oil wet.In this way not even a film of water is left on these metal surfaces.

EXAMPLE Using the apparatus as shown in FIG. I, wherein wall 4 ofwellbore 2 is permafrost, the wellbore is drilled using a water-basedrilling fluid weighing about eleven pounds per gallon so that in thestage of the completion process as represented by FIG. 1 interior 10 andannulus 5 are substantially filled with water-base drilling fluid.

Conventional cement is employed below opening plug 27 to achieve the.stage of the completion shown by FIG. 2. After this first cementingstep below apertures 9, the tool is opened and the remaining waterbasedrilling fluid is washed out of interior 10 and annulus 5 with freshwater which has a weight of 8.3 pounds per gallon. After a large volumeof fresh water (second liquid) is employed to wash most of the heavierwaterbase drilling fluid out of interior 10 and annulus 5, bypass wiper32 is inserted into interior l and forced downwardly into contact withopening plug 27 as shown in FIG. 3. Plug 27 is followed by an oil-basepacker fluid which weighs about ten pounds per gallon, the oil-basepacker fluid leaving bypass wiper 32 in the position shown in FIG. 3,passing by wiper 32, through apertures 9 and upwardly in annulus todisplace fresh water from annulus 5.

Efficient displacement of fresh water from annulus 5 is achieved becausethe oil-base fluid (third liquid) is heavier than the water (secondliquid). This would not be so if the oil-base liquid were used directlyto displace the heavier water-base drilling fluid (first liquid). Thus,by the use of the apparatus and method of this invention the heavywater-base drilling fluid is efficiently and substantially completelyremoved from interior l0 and annulus 5 leaving a nonfreezable oil-basefluid in interior 10 and annulus 5. Thus, upon carrying out the secondcementing step to emplace cement above level 26, if any liquid isbypassed by the cement it will be nonfreezable liquid.

After the emplacement of the third, nonfreezable, oil-base liquid ininterior It! and annulus 5 the second cementing step is carried outwherein cement is forced downwardly in interior 10 through apertures 9and upwardly in annulus 5 until cement has reached the'desired level inannulus 5 (if cementing is to be stopped below the earths surface) oruntil the cement reaches the earths surface. Upon pumping the desiredquantity of cement shutoff wiper 46 is employed to close apertures 9with sleeve 12 and to displace substantially all cement from interior 10into annulus 5 except for that cement which remains between the bottomof seat 118 and the top of shutoff wiper 46 plus any slight residualamount of cement above wiper 46.

Reasonable variations and modifications are possible within the scope ofthis disclosure without departing from the spirit and scope of thisinvention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows.

l. A well completion method in a wellbore comprising placing a string ofcasing in said wellbore, said casing having at an intermediate pointalong the length thereof a tool which can be opened to establishcommunication at the tool between the inside and outside of said casingand then closed to terminate such communication, said casing and toolcontaining a first liquid, placing cement below said tool, opening saidtool, washing residual first liquid out of the interior of said casingand tool with second liquid, displacing remaining second liquid from theinterior of said casing and tool with a third liquid, said second liquidweighing less per unit volume than said first liquid, said third liquidweighing no more per unit volume than said first liquid, displacing saidthird liquid fromsaid casing and tool with cement, and closing saidtool.

2. A method according to claim ll wherein said first liquid is awater-base drilling fluid which is heavier than said third liquid, andsaid third liquid is an oil-base liquid.

3. A method according to claim 2 wherein said second liquid is water andis lighter than said third liquid.

4. A method according to claim Slwherein said third liquid contains afreezing point depressant for transfer to any remaining second liquid. 7I

5. A method according to claim 2 wherein said third liquid contains anoil-wetting agent to render metal parts in said wellbore preferentiallyoil wet to prevent leaving an aqueous film thereon.

6. A method according to claim 1 wherein said second liquid contains athinner for decreasing the viscosity of said first liquid. i

7. A method according to claim I wherein a bypass wiper is employedbetween said second and third liquids.

8. A method according to claim 1 wherein said third liquid is moreviscous than said second liquid, and said third liquid is lighter thansaid first liquid.

9. A method according to claim 1 wherein said third liquid is lighterthan said first liquid, and said secondv third liquid.

1. A well completion method in a wellbore comprising placing a string ofcasing in said wellbore, said casing having at an intermediate pointalong the length thereof a tool which can be opened to establishcommunication at the tool between the inside and outside of said casingand then closed to terminate such communication, said casing and toolcontaining a first liquid, placing cement below said tool, opening saidtool, washing residual first liquid out of the interior of said casingand tool with second liquid, displacing remaining second liquid from theinterior of saiD casing and tool with a third liquid, said second liquidweighing less per unit volume than said first liquid, said third liquidweighing no more per unit volume than said first liquid, displacing saidthird liquid from said casing and tool with cement, and closing saidtool.
 2. A method according to claim 1 wherein said first liquid is awater-base drilling fluid which is heavier than said third liquid, andsaid third liquid is an oil-base liquid.
 3. A method according to claim2 wherein said second liquid is water and is lighter than said thirdliquid.
 4. A method according to claim 3 wherein said third liquidcontains a freezing point depressant for transfer to any remainingsecond liquid.
 5. A method according to claim 2 wherein said thirdliquid contains an oil-wetting agent to render metal parts in saidwellbore preferentially oil wet to prevent leaving an aqueous filmthereon.
 6. A method according to claim 1 wherein said second liquidcontains a thinner for decreasing the viscosity of said first liquid. 7.A method according to claim 1 wherein a bypass wiper is employed betweensaid second and third liquids.
 8. A method according to claim 1 whereinsaid third liquid is more viscous than said second liquid, and saidthird liquid is lighter than said first liquid.
 9. A method according toclaim 1 wherein said third liquid is lighter than said first liquid, andsaid second liquid is lighter than said third liquid.